1. Field of the Invention
The present invention relates to an apparatus for preventing an overload of an air conditioner and a method thereof, and more particularly to an apparatus for preventing an overload of an air conditioner and a method thereof, the apparatus and method being capable of preventing a continuous overload state of a compressor and damage of a compressor in the air conditioner having a plurality of compressors.
2. Description of the Related Art
Conventionally, an air conditioner includes a compressor for changing a coolant of a low-temperature and low-pressure gas state to a coolant of a high-temperature and high-pressure gas state; a condenser for changing the coolant of the high-temperature and high-pressure gas state to a coolant of a medium-temperature and high-pressure liquid state; an expansion device for changing the coolant of the medium-temperature and high-pressure liquid state to a coolant of a low-temperature and low-pressure liquid state; and a vaporizer for changing the coolant of the low-temperature and low-pressure liquid state to a coolant of a gas state.
In a heat pump type air conditioner, operations of indoor and outdoor heat exchangers vary with a cooling or heating mode. In the heating mode, the indoor heat exchanger acts as the condenser, and the outdoor heat exchanger acts as the vaporizer. Otherwise, in the cooling mode, the indoor heat exchanger acts as the vaporizer, and the outdoor heat exchanger acts as the condenser.
A recent air conditioner can vary capacity of a compressor on the basis of a cooling or heating load using a plurality of compressors having different capacities. FIG. 1 is a view illustrating a cooling cycle of a conventional heat pump type air conditioner having two compressors. The conventional air conditioner includes first and second compressors 11 and 12 having different capacities for compressing coolants to high-temperature and high-pressure gas coolants; check valves 11a and 12a for preventing backflow of the coolants compressed by the compressors 11 and 12; a four-way valve 13 for changing roles of heat exchangers by switching paths of the coolants passing through the first and second compressors 11 and 12; an outdoor heat exchanger 14 for condensing a coolant to a medium-temperature and high-pressure liquid coolant by performing heat exchange with the coolant and outdoor air; an expansion valve 15 for decompressing the coolant passing through the outdoor heat exchanger 14 to a low-temperature and low-pressure liquid coolant; an indoor heat exchanger 16 for vaporizing the coolant passing through the expansion valve 15 and performing heat exchange with the coolant and indoor air; and an accumulator 17 for supplying only a gas coolant to the first and second compressors 11 and 12 by separating the liquid coolant from a two-phase coolant passing through the indoor heat exchanger 16.
As shown in FIG. 2, an apparatus for preventing overloads of the first and second compressors 11 and 12, according to conventional techniques of preventing an overload of a heat pump, includes a controller 20 for controlling an operation of the air conditioner; first and second compressors 11 and 12 operated by currents supplied from the controller 20; and current cutoff units 41 and 42, connected between the controller 20 and the first and second compressors 11 and 12, for cutting off the currents supplied to the first and second compressors 11 and 12 when the first and second compressors 11 and 12 are in overload states. The current cutoff units 41 and 42 are turned off according to increasing inner temperatures of the compressors where the first and second compressors 11 and 12 are abnormally operated.
Capacitors 31a and 32a are connected between the controller 20 and the first and second compressors 11 and 12 to ensure sufficient electrostatic capacitances required for the operations of the first and second compressors 11 and 12.
In the conventional apparatus for preventing the overload of the heat pump, the current cutoff unit 41 connected to the first compressor 11 is turned off when the first compressor 11 is in an overload state. The current supplied from the controller 20 is then cut off to relieve the overload of the first compressor 11. If the current cutoff unit 41 is recovered after relieving the overload of the first compressor 11, it supplies the current from the controller 20 to the first compressor 11 to operate the first compressor 11.
Further, the current cutoff unit 42 connected to the second compressor 12 is turned off when the second compressor 12 is in the overload state. After relieving the overload of the second compressor 12, the current cutoff unit 42 supplies the current from the controller 20 to the second compressor 12 to re-operate the second compressor 12.
However, where an operation of one compressor is stopped due to its overload in the conventional apparatus for preventing the overload of the air conditioner, a liquid coolant can be inputted into an operating compressor because of differential pressure across the operating compressor. Thus, there is a problem in that the operating compressor can be damaged. Further, where the operating compressor is damaged, the overload state of the compressor is prolonged.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an apparatus for preventing an overload of an air conditioner and a method thereof, the apparatus and method being capable of preventing a continuous overload state of a compressor and hence damage of a compressor by relieving the overload state of the compressor and then re-operating a plurality of compressors after simultaneously stopping operations of the compressors when one of the compressors is in the overload state.
In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of an apparatus for preventing an overload of an air conditioner, comprising: a controller for controlling an operation of the air conditioner; a plurality of compressors being turned on/off in response to currents supplied from the controller; current feedback units for feeding back the currents, supplied to the compressors, to the controller when the compressors are in overload states; and a comparator installed in the controller for determining the overload states of the compressors on the basis of current differences between the currents inputted into the compressors and the currents fed back from the current feedback units.
In accordance with another aspect of the present invention, there is provided a method for preventing an overload of an air conditioner, comprising the steps of: a) sensing current differences between currents, supplied from a controller controlling an operation of the air conditioner to a plurality of compressors, and currents fed back to the controller; b) determining an overload state of a compressor according to the existence of a current difference sensed at the step a); c) simultaneously stopping operations of the compressors if at least one compressor is in an overload state as a result of the determination at the step b); and d) after stopping the operations of the compressors, re-operating the compressors, if the currents are appropriately supplied to the compressors at predetermined time intervals and the current differences between the currents supplied to the compressors and the currents fed back to the controller exist.